Short term fuel trims?

[strengthrehab]

So I was at the track (HPDE) and when I pulled off, the car was running rough. Earlier in the day, I went off into grass but car was fine afterward. There was some grass dust in the air intake (stock) box and filter.

Now, it is running rough with strong exhaust fumes.

No DTC's, no CEL.

Car idles at 750-850 rpm. Runs ok above 2500 rpm. Drove hone from track (2 hours) but couldn't drive in 6th.

Short term fuel trim is up to 25% on bank at idle. No misfire codes. No misfire noted during idle. Or 2500 rpm.

Any clue? O2 sensor?

I haven't pulled any plugs yet or done compression test.

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[Jay-rod427]

Both banks or just one? Check o2 readings, and maf readings for erratic behavior. Can't believe it hasn't set a cel yet. Flex learning could be bonkers as well.

 

[strengthrehab]

I have screen shots on phone from obd2 scans.

 

[Jay-rod427]

Use your Ngauge to read and log everything. I'd open a case with them as well.

 

[beefcake]

what do you mean by "went off into the grass"

 

[Jay-rod427]

Just saw your video. Car is definitely not happy.

 

[strengthrehab]

what do you mean by "went off into the grass"

Car spun coming out of a corner and I went off track.

It ran fine after this, though. I took it to the gas station and had another 2 track sessions after this happened. The last session started well, but times kept increasing. Then when I came off track for last time it was reacting this way.

 

[Jay-rod427]

Car spun coming out of a corner and I went off track.

It ran fine after this, though. I took it to the gas station and had another 2 track sessions after this happened. The last session started well, but times kept increasing. Then when I came off track for last time it was reacting this way.

Was the flex fuel alcohol learning flag checked and done by the time you got back out on the track? Otherwise the alcohol learn could be way off if racing while it's trying to complete the % learn. Go to a gas station and top off the tank. This will prompt the flex fuel learning to initiate again. Let it learn 5 mins idle, then normal light driving until it's flagged as learned.

 

[strengthrehab]

I'd assume as I had 1/4 tank of e85 in the tank early in the day. Filled up with 93, drove an hour to the track, ran 2 sessions, refilled with 93, then drove 5 mins back to the track and another session (30 mins) on track before the last track session

 

[Jay-rod427]

On the ngauge is a learned alcohol flag its a 0 when learning, and a 1 when complete. No matter what you put in the tank it initiates the learning procedure. And needs some time/miles to complete and get an accurate %. Which directly affects the fuel trims and run quality. I'm guessing this is what went wonky. Do the previous posted to re initiate learning and see how it runs.

 

[Bluemustang]

I read somewhere that this is why it's best to change fuel types when you're almost near empty. Something about the fuel level getting low enough that it trips the re-learning process. I would always not care and just fill up with 93 or E85 regardless of how much is left but a few times I have had some issues. So now from now on I bring it as close to empty as possible before changing fuels.

 

[strengthrehab]

On the ngauge is a learned alcohol flag its a 0 when learning, and a 1 when complete. No matter what you put in the tank it initiates the learning procedure. And needs some time/miles to complete and get an accurate %. Which directly affects the fuel trims and run quality. I'm guessing this is what went wonky. Do the previous posted to re initiate learning and see how it runs.

I'll try it. Can I do the same by loading another tune?

 

[Jay-rod427]

I'll try it. Can I do the same by loading another tune?

yes.

 

[Jay-rod427]

I read somewhere that this is why it's best to change fuel types when you're almost near empty. Something about the fuel level getting low enough that it trips the re-learning process. I would always not care and just fill up with 93 or E85 regardless of how much is left but a few times I have had some issues. So now from now on I bring it as close to empty as possible before changing fuels.

I've topped off with as little as 5 gals and it initiates relearn just fine. It's not how low, but how much change in fuel level since last ignition cycle.

 

[Bluemustang]

I've topped off with as little as 5 gals and it initiates relearn just fine. It's not how low, but how much change in fuel level since last ignition cycle.

I've done the same as you. Just sharing my own experience. Nevertheless that’s good to know, thanks for sharing.

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